All sorts. Three come to mind. Two of them are sort of the same, I suppose. I was heading home from primary school, as part of my "growing up" process I was now allowed to do some of this myself rather than be escorted home by Dad. he'd set off to meet me, and I'd set off before he'd got to School and we would meet half-way. Anyway, this particular day, I can't think why, but I decided to take a different route home through a small wood. And so my Dad never did meet me, I got back home without him. Goodness only know how much he was worried, but it was enough so that there was an (anonymous) announcement about it in School the next day...
Another time, I went to spend the afternoon with a friend, but at no point told my parents where I'd gone... again I was all safe but I'm fairly sure that they were on the verge of calling the police, if not having done it already... I know Mum was upset and angry when I got home so she must have been super scared...
Something that really qualifies as stupid, again at Primary School. There is the main road between my house and the school and this one time I just crossed it without looking at all. I'm told that a truck missed me by inches, but I didn't notice... closest I've ever come to death.
I don't even think these are the most stupid incidents (stepping off a bus while it was still moving; falling forward deliberately while trying to demonstrate that this was possible without putting hands in front of me to stop my fall -- I didn't use my hands, but on the way down I thought, "Hang on, the first part that is going to hit the ground is my OWWWWW!!!) , but perhaps they're enough of a taster for now.